This invention relates to heterocyclic compounds, more particularly to compounds represented by the general formula (I) that have a nitric oxide synthase (NOS) inhibiting action to suppress the production of nitric oxide (NO) and thereby prove effective against disorders and diseases in which excessive NO or NO metabolites are supposedly involved, namely, cerebrovascular diseases [cerebral hemorrhage, subarachnoid hemorrhage, cerebral infarction (atherothromobotic infarction, lacunar infarction and cardiogenic embolism), transient ischemic attack and cerebral edema], traumatic brain injury, spinal injury, pains [headache (migraine, tension headache, cluster headache and chronic paroxysmal headache)], Parkinson""s disease, Alzheimer""s disease, seizure, and morphine tolerance or dependence. The invention also relates to possible tautomers, stereoisomers and optically active forms of said compounds, as well as pharmaceutically acceptable salts thereof. The invention further relates to preventives and therapeutics that contain said compounds or pharmaceutically acceptable salts as active ingredients.
The number of deaths from cerebrovascular diseases in Japan had increased until 1970 when it began to decline mostly due to the improvement in their acute-phase therapy. Nevertheless, cerebrovascular diseases remain the second leading cause of death among adult diseases, next only to cancers. As for the incidence of cerebrovascular diseases, many statistical surveys indicate that it is generally constant and in view of the fact that the number of elderly persons will increase at an uncomparably faster speed in Japan than any other country in the world, the number of patients suffering from cerebrovascular diseases is estimated to increase rather than decrease in the future. The declining mortality and the growing population of aged people combine to increase the cases of cerebrovascular diseases in the chronic phase and this has presented with a national problem not only from the aspects of individual patients and society at large but also from the viewpoint of medical economics since patients with chronic cerebrovascular disease are inevitably involved in long-term care. In cerebral infarction that accounts for most cases of cerebrovascular diseases, cerebral arteries are occluded and blood deficit starting at the blocked site extends to the peripheral site, causing an ischemic state. The symptoms of cerebral infarction in the chronic phase are in almost all cases derived from the loss of neurons and it would be extremely difficult to develop medications or established therapeutic methods for achieving complete recovery from those symptoms. Therefore, it is no exaggeration that the improvement in the performance of treatments for cerebral infarction depends on how patients in an acute phase can be treated with a specific view to protecting neurons and how far their symptoms can be ameliorated in the acute phase. However, most of the medications currently in clinical use are antiplatelet drugs, anticoagulants and thrombolytics and none of these have a direct nerve protecting action (see Kazuo MINEMATSU et al., xe2x80x9cMEDICINAxe2x80x9d, published by Igaku Shoin, 32, 1995 and Hidehiro MIZUSAWA et al., published by Nankodo, xe2x80x9cNaikaxe2x80x9d 79, 1997). Therefore, it is desired to develop a drug that provides an effective therapy for cerebrovascular diseases, in particular cerebral infarction, by working in an entirely novel and different mechanism of action from the conventional medications.
A presently dominant theory based on genetic DNA analyses holds that NOS exists in at least three isoforms, namely, calcium-dependent nNOS (type 1) which is present constitutively in neurons, calcium-dependent eNOS (type 3) which is present constitutively in vascular endothelial cells, and apparently calcium-independent iNOS (type 2) which is induced and synthesized by stimulation with cytokines and/or lipopolysaccharides (LPS) in macrophages and many other cells (Nathan et al., FASEB J. 16, 3051-3064, 1992; Nagafuji et al., Mol. Chem. Neuropathol. 26, 107-157, 1995).
A mechanism that has been proposed as being most probable for explaining the brain tissue damage which accompanies cerebral ischemia is a pathway comprising the sequence of elevation in the extracellular glutamic acid level, hyperactivation of glutamic acid receptors on the post-synapses, elevation in the intracellular calcium level and activation of calcium-dependent enzymes (Siesjxc3x6, J. Cereb. Blood Flow Metab. 1, 155-185, 1981; Siesjxc3x6, J. Neurosurg. 60, 883-908, 1984; Choi, Trends Neurosci. 11, 465-469, 1988; Siesjxc3x6 and Bengstsson, J. Cereb. Blood Flow Metab. 9, 127-140, 1989). As already mentioned, nNOS is calcium-dependent, so the inhibition of hyperactivation of this type of NOS isoforms would contribute to the neuro-protective effects of NOS inhibitors (Dawson et al., Annals Neurol. 32, 297-311, 1992). As a matter of fact, the mRNA level of nNOS and the number of nNOS containing neurons start to increase early after focal cerebral ischemia in rats and their temporal alterations coincide with the development of infarction (Zhang et al., Brain Res. 654, 85-95, 1994). In an experiment with a mouse model of focal cerebral ischemia using NG-nitro-L-arginine (L-NA) which is a NOS inhibitor, the percent inhibition of nNOS activity and the percent reduction of infarct volume correlated to each other at least in a dose range that produced a recognizable infarct volume reductive action (Carreau et al., Eur. J. Pharmacol. 256, 241-249, 1994). Further in addition, it has been reported that in nNOS knockout mice, the infarct volume observed after focal cerebral ischemia is significantly smaller than that in the control (Huang et al., Science 265, 1883-1885, 1994).
Referring now to NO, it is at least one of the essences of endothelium-derived relaxing factor (EDRF) and, hence, is believed to take part in the adjustment of the tension of blood vessels and the blood flow (Moncada et al., Pharmacol. Rev. 43, 109-142, 1991). As a matter of fact, it was reported that when rats were administered high doses of L-NA, the cerebral blood flow was found to decrease in a dose-dependent manner as the blood pressure increased (Toru MATSUI et al., Jikken Igaku, 11, 55-60, 1993). The brain has a mechanism by which the cerebral blood flow is maintained at a constant level notwithstanding the variations of blood pressure over a specified range (which is commonly referred to as xe2x80x9cautoregulation mechanismxe2x80x9d) (xe2x80x9cNOSOTCHU JIKKEN HANDBOOKxe2x80x9d, complied by Keiji SANO, published by IPC, 247-249, 1990). The report of Matsui et al. suggests the failure of this xe2x80x9cautoregulation mechanismxe2x80x9d to operate. Therefore, if eNOS is particularly inhibited beyond a certain limit in an episode of brain ischemia, the cerebral blood vessel will contract and the cerebral blood flow will decrease, thereby aggravating the dynamics of microcirculation, possibly leading to an expansion of the ischemic lesion. It was also reported that in eNOS knockout mice, the infarct observed after focal cerebral ischemia was larger than that in the control but could be reduced significantly by administration of L-NA (Huang et al., J. Cereb. Blood Flow Metab. 16, 981-987, 1996). These reports show that eNOS-derived NO probably works protectively on the brain tissue through the intermediary of a vasodilating action, a platelet aggregation suppressing action and so forth.
The present inventors previously found that L-NA, already known to be a NOS inhibitor, possessed ameliorative effects on the brain edema and cerebral infarction following phenomena that developed after experimental cerebral ischemia (Nagafuji et al., Neurosci. Lett. 147, 159-162, 1992; Japanese Patent Public Disclosure No. 192080/1994), as well as necrotic neuronal cell death (Nagafuji et al., Eur. J. Pharmacol. Env. Tox. 248, 325-328, 1993). On the other hand, relatively high doses of NOS inhibitors have been reported to be entirely ineffective against ischemic brain damage and sometimes aggravating it (Idadecola et al., J. Cereb. Blood Flow Metab. 14, 175-192, 1994; Toshiaki NAGAFUJI and Toru MATSUI, Jikken Igaku, 13, 127-135, 1995; Nagafuji et al., Mol. Chem. Neuropathol. 26, 107-157, 1995). It should, however, be stressed that as a matter of fact, all papers that reported the changes of NO or NO-related metabolites in the brain and blood in permanent or temporary cerebral ischemic models agreed in their results to show the increase in the levels of those substances (Toshiaki NAGAFUJI and Toru MATSUI, Jikken Igaku, 13, 127-135, 1995; Nagafuji et al., Mol. Chem. Neuropathol. 26, 107-157, 1995).
One of the reasons for explaining the fact that conflicting reports have been made about the effectiveness of NOS inhibitors in cerebral ischemic models would be the low selectivity of the employed NOS inhibitors for nNOS. As a matter of fact, no existing NOS inhibitors including L-NA and NG-nitro-L-arginine methyl ester (L-NAME) have a highly selective inhibitory effect on a specific NOS isoform (Nagafuji et al. Neuroreport 6, 1541-1545, 1995; Nagafuji et al. Mol. Chem. Neuropathol. 26, 107-157, 1995). Therefore, it may well be concluded that desirable therapeutics of ischemic cerebrovascular diseases should have a selective inhibitory effect on nNOS (Nowicki et al., Eur. J. Pharmacol. 204, 339-340, 1991; Dawson et al., Proc. Natl. Acad. Sci. USA 88, 6368-6371, 1991; Iadecola et al., J. Cereb. Blood Flow Metab. 15, 52-59, 1995; Iadecola et al., J. Cereb. Blood Flow Metab. 15, 378-384, 1995; Toshiaki NAGAFUJI and Toru MATSUI, Jikken Igaku 13, 127-135, 1995; Nagafuji et al., Mol. Chem. Neuropathol. 26, 107-157, 1995; Iadecola et al., Am. J. Physiol. R286-R292, 1995).
It has also been suggested that nNOS inhibitors have the potential for use as therapeutics of traumatic brain injuries (Oury et al., J. Biol. Chem. 268, 15394-15398, 1993; MacKenzie et al., Neuroreport 6, 1789-1794, 1995; Mesenge et al., J. Neurotrauma. 13, 11-16, 1996; Wallis et al., Brain Res., 710, 169-177, 1996), headache and other pains (Moore et al., Br. J. Pharmacol. 102, 198-202, 1991; Olesen., Trends Pharmacol. 15, 149-153, 1994), Parkinson""s disease (Youdim et al., Advances Neurol. 60, 259-266, 1993; Schulz et al., J. Neurochem. 64, 936-939, 1995; Hantraye et al., Nature Medicine 2, 1017-1021, 1996), Alzheimer""s disease (Hu and EI-FaKahany, Neuroreport 4, 760-762, 1993 Meda et al., Nature 374, 647-650, 1995), seizure (Rigaud-Monnet et al., J. Cereb. Blood Flow Metab. 14, 581-590, 1994), and morphine tolerance and dependence (Kolesnikov et al., Eur. J. Pharmacol. 221, 399-400, 1992; Cappendijk et al., Neurosci. Lett. 162, 97-100, 1993).
The NOS inhibitors so far reported to have a certain degree of selectivity for nNOS are NG-cyclopropyl-L-arginine (L-CPA)(Lamberte et al., Eur. J. Pharmacol. 216, 131-134, 1992), L-NA (Furfine et al., Biochem. 32, 8512-8517, 1993), S-methyl-L-thiocitrulline (L-MIN) (Narayanan and Griffith, J. Med. Chem. 37, 885-887, 1994; Furfine et al., J. Biol. Chem. 37, 885-887, 1994; Furfine et al. J. Biol. Chem. 269, 26677-26683, 1994; WO95/09619; Narayanan et al., J. Biol. Chem. 270, 11103-11110, 1995; Nagafuji et al., Neuroreport 6, 1541-1545, 1995), S-ethyl-L-thiocitrulline (L-EIN) (Furfine et al., J. Biol. Chem. 269, 26677-26683, 1994; WO95/09619; Narayanan et al.,J. Biol. Chem. 270, 11103-11110, 1995), and ARL 17477 (Gentile et al., WO95/05363; Zhang et al., J. Cereb. Blood Flow Metab., 16, 599-604, 1996). WO96/18608 lists compounds showing nNOS inhibiting activity.
An object of the present invention is to provide novel compounds that have a selective inhibitory effect on calcium-dependent nNOS which is present constitutively in the brain, particularly in neurons, and which are useful as therapeutics of cerebrovascular diseases [cerebral hemorrhage, subarachnoid hemorrhage, cerebral infarction (atherothrombotic infarction, lacunar infarction and cardiogenic embolism), transient ischemic attack and cerebral edema], traumatic brain injury, spinal injury, pains [headache (migraine, tension headache, cluster headache and chronic paroxysmal headache)], Parkinson""s disease, Alzheimer""s disease, seizure, and morphine tolerance or dependence.
As a result of the intensive studies made in order to attain the stated object, the present inventors found that heterocyclic compounds represented by the general formula (1), or possible tautomers, stereoisomers and optically active forms of said compounds, as well as pharmaceutically acceptable salts thereof have an nNOS inhibitory action or selectivity greater than any existing NOS inhibitors, thereby exhibiting marked effectiveness as therapeutics of cerebrovascular diseases (especially as therapeutics of occlusive cerebrovascular diseases): 
(wherein
R1 is an optionally substituted aminoalkyl group having 1-6 carbon atoms in the alkyl moiety;
R2 is a hydrogen atom, a lower alkyl group or a halogen atom;
R3 is an optionally substituted lower alkyl group, SR4, OR4 or NR5R6 provided that R4 is a lower alkyl group that may be substituted by a halogen atom and R5 and R6, which may be the same or different, represent a hydrogen atom, a lower alkyl group or a nitro group or, when taken together, may form a 3- to 6-membered ring; and
Ar is an optionally substituted 5- or 6-membered aromatic heterocyclic group).
The present invention has been accomplished on the basis of this finding.
The aminoalkyl group having 1-6 carbon atoms in the alkyl moiety means an aminoalkyl group having the alkyl moiety of which is a straight-chained alkyl having 1-6 carbon atoms or an aminoalkyl group having the alkyl moiety of which is a cyclic alkyl having 3-6 carbon atoms, and examples include an aminomethyl group, a 2-aminoethyl group, a 3-aminopropyl group, a 4-aminobutyl group,a 5-aminopentyl group, a 6-aminohexyl group, a 1-aminocyclopropyl group, a 2-aminocyclopropyl group, a 1-aminocyclobutyl group, a 2-aminocyclobutyl group, 3-aminocyclobutyl group, a 1-aminocyclopentyl group, a 2-aminocyclopentyl group, a 3-aminocyclopentyl group, a 1-aminocyclhexyl group, a 2-aminocyclohexyl group, a 3-aminocyclohexyl group, a 4-aminocyclohexyl group, etc.
The lower alkyl group means a straight-chained alkyl group having 1-6 carbon atoms or a branched or cyclic alkyl group having 3-8 carbon atoms, and examples include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an i-propyl group, an i-butyl group, a sec-butyl group, a tert-butyl group, an i-pentyl group, a neopentyl group, a tert-pentyl group, an i-hexyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, etc.
The halogen atom is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.
The 5- or 6-membered aromatic heterocyclic group contains at least one nitrogen atom and may optionally contain an oxygen atom or a sulfur atom and examples include a pyrrol-1-yl group, a pyrrol-2-yl group, a pyrrol-3-yl group, a pyrazol-1-yl group, a pyrazol-3-yl group, a pyrazol-4-yl group, an imidazol-1-yl group, an imidazol-2-yl group, an imidazol-4-yl group, a 1,2,3-triazol-1-yl group, a 1,2,4-triazol-1-yl group, a 1,2,4-triazol-3-yl group, a 1H-tetrazol-1-yl group, an isoxazol-3-yl group, an isoxazol-4-yl group, an isoxazol-5-yl group, an isothiazol-3-yl group, an isothiazol-4-yl group, an isothiazol-5-yl group, an oxazol-2-yl group, an oxazol-4-yl group, an oxazol-5-yl group, a thiazol-2-yl group, a thiazol-4-yl group, a thiazol-5-yl group, a pyridin-2-yl group, a pyridin-3-yl group, a pyridin-4-yl group, a pyridazin-3-yl group, a pyridazin-4-yl group, a pyrimidin-2-yl group, a pyrimidin-4-yl group, a pyrimidin-5-yl group, a pyrazin-2-yl group, a 1,2,4-triazin-3-yl group, a 1,2,4-triazin-5-yl group, a 1,2,4-triazin-6-yl group, a 1,3,5-triazin-2-yl group, etc.
The substituent in R1 and Ar may be exemplified by a lower alkyl group, a phenyl group, a benzyl group and a phenethyl group.
The substituent in R3 may be exemplified by a halogen atom, a lower alkoxy group and a lower alkylthio group.
The lower alkoxy group means a straight-chained alkoxy group having 1-6 carbon atoms or a branched or cyclic alkoxy group having 3-8 carbon atoms, and examples include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentoxy group, an n-hexoxy group, an i-propoxy group, an i-butoxy group, a sec-butoxy group, a tert-butoxy group, an i-pentoxy group, a neopentoxy group, a tert-pentoxy group, an i-hexoxy group, a cyclopropoxy group, a cyclobutoxy group, a cyclopentoxy group, a cyclohexoxy group, a cycloheptoxy group, a cyclooctoxy group, etc.
The lower alkylthio group is a straight-chained alkylthio group having 1-6 carbon atoms or a branched or cyclic alkylthio group having 3-8 carbon atoms, and examples include a methylthio group, an ethylthio group, an n-propylthio group, an n-butylthio group, an n-pentylthio group, an n-hexylthio group, an i-propylthio group, an i-butylthio group, a sec-butylthio group, a tert-butylthio group, an i-pentylthio group, a neopentylthio group, a tert-pentylthio group, an i-hexylthio group, a cyclopropylthio group, a cyclobutylthio group, a cyclopentylthio group, a cyclohexylthio group, a cycloheptylthio group, a cyclooctylthio group, etc.
The optionally substituted lower alkyl group as R3 is preferably a lower alkyl group having 1-4 carbon atoms that may be substituted by a halogen atom, a lower alkoxy group or a lower alkylthio group, and examples include a methyl group, a fluoromethyl group, a methoxymethyl group, an ethoxymethyl group, a methylthiomethyl group, an ethylthiomethyl group, an ethyl group, a 2-fluoroethyl group, a 2,2,2-trifluoroethyl group, a 2-chloroethyl group, a 2-methoxyethyl group, a 2-methylaminoethyl group, an n-propyl group, an i-propyl group, a 1-methylthiopropyl group, an n-butyl group, an i-butyl group, etc.
A preferred example of SR4 as R3 is a lower alkylthio group having 1-3 carbon atoms that may be substituted by a halogen atom, as exemplified by a methylthio group, an ethylthio group, a 2-fluoroethylthio group, a 2,2,2-trifluoroethylthio group, a 2-chloroethylthio group, an n-propylthio group, an i-propylthio group, etc.; an ethylthio group is particularly preferred.
A preferred example of OR4 as R3 is a lower alkoxy group having 1-3 carbon atoms that may be substituted by a halogen atom, as exemplified by a methoxy group, an ethoxy group, a 2-fluoroethoxy group, a 2,2,2-trifluoroethoxy group, a 2-chloroethoxy group, an n-propoxy group, an i-propoxy group, etc.
The lower alkyl group as R5 and R6 is preferably a lower alkyl having 1-3 carbon atoms.
The cyclic group that may form a 3- to 6-membered ring of R5 and R6 when combined together is preferably a 5- or 6-membered heterocyclic group containing at least one nitrogen atom.
A preferred example of NR5R6 as R3 is a primary or secondary amino group that may be substituted by a lower alkyl group of 1-3 carbon atoms or a nitro group or a 5- or 6-membered heterocyclic group containing at least one nitrogen atom, as exemplified by an amino group, a methylamino group, an ethylamino group, an n-propylamino group, an i-propylamino group, a dimethylamino group, an ethylmethylamino group, a nitroamino group, a pyrrolidin-1-yl group, a piperidino group, a morpholino group, a pyrrol-1-yl group, a pyrrol-2-yl group, a pyrrol-3-yl group, a pyrazol-1-yl group, a pyrazol-3-yl group, a pyrazol-4-yl group, an imidazol-1-yl group, an imidazol-2-yl group, an imidazol-4-yl group, a 1,2,3-triazol-1-yl group, a 1,2,4-triazol-1-yl group, a 1,2,4-triazol-3-yl group, a 1H-tetrazol-1-yl group, a pyridin-2-yl group, a pyridin-3-yl group, a pyridin-4-yl group, a pyridazin-3-yl group, a pyridazin-4-yl group, a pyrimidin-2-yl group, a pyrimidin-4-yl group, a pyrimidin-5-yl group, a pyrazin-2-yl group, a 1,2,4-triazin-3-yl group, a 1,2,4-triazin-5-yl group, a 1,2,4-triazin-6-yl group, a 1,3,5-triazin-2-yl group, etc.
A preferred example of R1 is an aminoalkyl group the alkyl moiety of which is a straight-chained alkyl having 1-3 carbon atoms and an aminomethyl group is particularly preferred.
A preferred example of R2 is a hydrogen atom or a lower alkyl group and a hydrogen atom or a methyl group is particularly preferred.
A preferred example of R3 is SR4, with a lower alkylthio group being more preferred and an ethylthio group being particularly preferred.
A preferred example of Ar is a 5-membered aromatic heterocyclic group; a more preferred example is an aromatic heterocyclic group containing a nitrogen atom, and a pyrrol-1-yl group and a pyrazol-1-yl group being particularly preferred.
Except for R2 and Ar, the benzene nucleus is preferably m-substituted.
The preferred examples of the compound represented by the general formula (1) include N-(3-aminomethyl-4-(pyrazol-1-yl)phenyl)-S-ethylisothiourea, N-(3-aminomethyl-4-(pyrrol-1-yl)phenyl)-S-ethylisothiourea and N-(3-aminomethyl-2-methyl-4-(pyrazol-1-yl)phenyl)-S-ethylisothiourea.
The compounds of the present invention which are represented by the general formula (1) can be synthesized by different methods depending on the specific type of R3 and exemplary methods are as follows. 
In the above formulas (2)-(16), R1 is an optionally substituted aminoalkyl group the alkyl moiety of which has 1-6 carbon atoms, R2 is a hydrogen atom, a lower alkyl group or a halogen atom, R4 is a lower alkyl group that may be substituted by a halogen atom, R7 is an optionally substituted lower alkyl group, R8 is a tert-butoxycarbonyl group or a benzyloxycarbonyl group, R9 and R10 which may be the same or different represent a hydrogen atom or a lower alkyl group or, when taken together, may form a 3- to 6-membered ring, Ar is an optionally substituted 5- or 6-membered aromatic heterocyclic group, and L is a leaving group such as a chlorine atom, a bromine atom, an iodine atom, a trifluoromethanesulfonyloxy group, a p-toluenesulfonyloxy group or a methanesulfonyloxy group.
Among the compounds represented by the formula (1), a compound represented by the formula (5) wherein R3 is R7 can be synthesized by a process that starts with a compound represented by the formula (2) and which gives a compound represented by the formula (4) as an intermediate.
Specifically, a compound represented by the formula (2) and a compound represented by the formula (3) are reacted in the presence or absence of 4-dimethylaminopyridine in an inert solvent such as an alcohol (e.g. methanol, ethanol or i-propanol) or chloroform, methylene chloride, 1,2-dichloroethane, toluene or dimethylformamide, preferably in methylene chloride, at a temperature between 0xc2x0 C. and the boiling point of the reaction mixture, preferably at room temperature, thereby giving a compound represented by the formula (4).
The resulting compound represented by the formula (4) has an amidino protecting group that is represented by R8 and this protective group is removed under ordinary conditions to produce a compound represented by the formula (5).
The reaction for removing the amidino protecting group depends on the type of the protective group. If it is a tert-butoxycarbonyl group, the reaction is preferably performed either in an inert solvent such as methanol, ethanol or 1,4-dioxane or in a solvent-free condition at a temperature between 0xc2x0 C. and room temperature using a deprotective agent such as trifluoroacetic acid, hydrochloric acid, sulfuric acid or methanesulfonic acid. It is particularly preferred to use trifluoroacetic acid at room temperature under anhydrous conditions.
If the amidino protecting group is a benzyloxycarbonyl group, it is removed by catalytic reduction reaction which can be performed with palladium-carbon or Raney""s nickel or platinum oxide as a catalyst in an inert solvent such as ethanol, methanol, ethyl acetate, acetic acid or 1,4-dioxane, preferably in ethanol or methanol, under a hydrogen atmosphere at a temperature between room temperature and the boiling point of the reaction mixture, preferably at room temperature.
Among the compounds represented by the formula (1), a compound represented by the formula (8) wherein R3 is SR4 can be synthesized by a process that starts with a compound represented by the formula (2) and which gives a compound represented by the formula (6) as an intermediate.
Specifically, a compound represented by the formula (2) is reacted with benzoyl isothiocyanate in an inert solvent such as tetrahydrofuran, chloroform, methylene chloride or dimethylformamide at a temperature between xe2x88x9220xc2x0 C. and the boiling point of the reaction mixture, preferably in acetone at room temperature. If necessary, the reaction mixture is concentrated after the end of the reaction and is further subjected to reaction in an inert solvent such as methanol in the presence of an inorganic base such as potassium carbonate or sodium hydroxide at a temperature between 0xc2x0 C. and the boiling point of the reaction mixture, preferably in methanol in the presence of potassium carbonate at room temperature, thereby giving a compound represented by the formula (6).
The compound represented by the formula (6) can also be obtained by performing reaction on the compound of the formula (2) in accordance with the method of T. Makino et al. (WO96/18608).
Specifically, the compound represented by the formula (2) is first reacted with thiophosgene in the presence of an inorganic base such as calcium carbonate or potassium carbonate or an organic base such as triethylamine or 4-dimethylaminopyridine in an inert solvent such as chloroform, methylene chloride, water or dimethylformamide at a temperature between 0xc2x0 C. and the boiling point of the reaction mixture, preferably in the presence of 4-dimethylaminopyridine in methylene chloride at room temperature and subsequently treated with conc. aqueous ammonia or saturated ammonia in methanol to give the compound of the formula (6).
The compound of the formula (6) can also be obtained by first reacting the compound of the formula (2) with benzoyl chloride or ammonium thiocyanate in an inert solvent such as acetone at a temperature between room temperature and the boiling point of the reaction mixture, preferably at room temperature, then heating the reaction mixture under reflux together with 10% sodium hydroxide solution.
In the next step, the compound of the formula (6) is reacted with a compound represented by the formula (7) in an inert solvent such as acetonitrile, acetone, 1,4-dioxane, methanol or ethanol at a temperature between room temperature and the boiling point of the reaction mixture, preferably in acetonitrile, as the reaction mixture is heated under reflux, thereby producing a compound represented by the formula (8).
Among the compounds represented by the formula (1), a compound represented by the formula (10) wherein R3 is OR4 can be synthesized by the following process starting with a compound represented by the formula (2).
The compound of the formula (2) is reacted with cyano bromide and a suitable type of alcohol represented by the formula (9) at a temperature between 0xc2x0 C. and the boiling point of the reaction mixture, preferably at room temperature, to produce the compound represented by the formula (10).
Among the compounds represented by the formula (1), a compound represented by the formula (13) wherein R3 is NR9R10 can be synthesized by a process that starts with a compound represented by the formula (2) and which gives a compound represented by either the formula (12) or (14) as an intermediate.
Specifically, the compound represented by the formula (2) is reacted with a compound represented by the formula (11) in accordance with the method of M. A. Poss (Tetrahedron Lett. 33, 5933-5936, 1992), thereby producing a compound of the formula (12), and the t-butoxycarbonyl protecting group is removed to yield a compound represented by the formula (13).
Alternatively, a compound represented by the formula (6) is converted to a compound represented by the formula (14) in accordance with the method of C. A. Maryanoff et al. (J. Org. Chem. 51, 1882-1884, 1986) and then reacted with an amine represented by the formula (15) so as to yield a compound represented by the formula (13).
Among the compounds represented by the formula (1), a compound represented by the formula (16) wherein R3 is NHNO2 can be synthesized by the following process starting with the compound of the formula (2).
The compound represented by the formula (2) is reacted with N-methyl-Nxe2x80x2-nitro-N-nitrosoguanidine in an inert solvent such as acetonitrile, ethanol, methanol or water, preferably in acetonitrile, at a temperature between room temperature and the boiling point of the reaction mixture, preferably at room temperature, in the optional presence of added triethylamine or acetic acid, thereby producing the compound of the formula (16).
If, in the process of synthesizing the compounds represented by the above formulas (4), (5), (6), (8), (10), (12), (13), (14) and (16), there occurs a substituent that needs a protective group, a protecting reaction and a deprotecting reaction are performed in accordance with the type of the substituent. In principle, both reactions can be performed by the methods described in Greene and Wuts, xe2x80x9cPROTECTIVE GROUPS IN ORGANIC SYNTHESISxe2x80x9d, 2nd Edition, John Wiley and Sons Inc. For example, if the substituent that needs a protective group is a primary or secondary amino group, suitable protective groups include a tert-butoxycarbonyl group, a benzyloxycarbonyl group and a trifluoroacetyl group.
An amino group protecting reaction, for example, tert-butylcarbonylation, can be accomplished by reaction with di-tert-butyl dicarbonate in an inert solvent such as an alcohol (e.g. methanol, ethanol or i-propanol) or methylene chloride, dimethylformamide or 1,4-dioxane in the presence of an organic base such as triethylamine or 4-dimethylaminopyridine at a temperature between 0xc2x0 C. and room temperature. Another amino group protecting reaction such as benzyloxycarbonylation can be accomplished by reaction with benzyl chlorocarbonate in an inert solvent such as methylene chloride in the presence of an organic base such as triethylamine or 4-dimethylaminopyridine at a temperature between 0xc2x0 C. and room temperature. Yet another amino group protecting reaction such as trifluoroacetylation can be accomplished by reaction with trifluoroacetic anhydride in an inert solvent such as methylene chloride in the presence of an organic base such as triethylamine or pyridine at a temperature between 0xc2x0 C. and room temperature.
Referring to the amino group deprotecting reaction, if the protective group is a tert-butoxycarbonyl group or a benzyloxycarbonyl group, the reaction can be performed under the same conditions as the reaction for removing the amidino protecting group. In the case of another protective group such as a trifluoroacetyl group, the deprotecting reaction can be accomplished either by reaction with potassium carbonate in methanol at room temperature or by reaction in 4 N HCl at 60xc2x0 C.
If the compounds of the invention which are represented by the general formula (1) have asymmetric carbons in their structure, the pure forms of their stereoisomers and optically active forms can be obtained by known techniques in the art, such as chromatography on optical isomer separating columns and fractional crystallization.
Pharmaceutically acceptable salts of the compounds of the invention which are represented by the general formula (1) may be of any types as long as they are pharmaceutically acceptable salts and typical examples include salts with inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid and hydroiodic acid, salts with organic acids such as formic acid, acetic acid, fumaric acid and tartaric acid, salts with alkali metals such as sodium and potassium, and salts with alkaline earth metals such as calcium and magnesium.
The compounds of the invention or salts thereof may be formulated with suitable excipients, adjuvants, lubricants, antiseptics, disintegrators, buffering agents, binders, stabilizers, wetting agents, emulsifiers, coloring agents, flavoring agents, fragrances, etc. to form tablets, granules, subtilized granules, powders, capsules, syrups, elixirs, suspensions, emulsions, injections, etc. for oral or parenteral administration. When the cerebrovascular diseases to be treated are in a hyperacute phase (immediately after the stroke), an acute phase (from the stroke to 2 or 3 days later) or in a subacute phase (2 or 3 days up to 2 weeks after the stroke), it is anticipated that administration is effected primarily by intramuscular or intravenous injection. In addition, oral administration may be performed in a chronic phase (the third week after stroke and onward) if the patient admits ingestion.
The compounds of the invention or salts thereof may be administered in doses that vary with the physical constitution of the patient, his or her age, physical condition, the severity of the disease, the time of lapse after the onset of the disease and other factors; typical daily doses are anticipated to range from 0.1 to 100 mg/body. It should generally be noted that even if the same dose is administered, the plasma concentration may sometimes vary considerably between patients; hence, an optimal dose of the drug should ideally be determined for each patient on the basis of a monitored plasma concentration of the drug.
If the compounds of the invention or salts thereof are to be formulated as preparations for internal application, lactose, sucrose, sorbitol, mannitol, starches such as potato starch or corn starch, starch derivatives and common additives such as cellulose derivatives or gelatin are suitably used as vehicles, with lubricants such as magnesium stearate, carbowaxes and polyethylene glycol being optionally added concurrently; the resulting mixtures may be formulated in the usual manner into granules, tablets, capsules or other forms suitable for internal application.
If the compounds of the invention or salts thereof are to be formulated as aqueous preparations, effective amounts of the principal ingredients may be dissolved in distilled water for injection, with antioxidants, stabilizers, dissolution aids, buffering agents, preservatives, etc. added as required and, after complete solutions are formed, they are filtered, filled into ampules and sealed in the usual manner and sterilized by a suitable medium such as high-pressure vapor or dry heat so as to prepare injections.
If the compounds of the invention or salts thereof are to be formulated as lyophilized preparations, aqueous solutions having the principal ingredients dissolved in distilled water for injection may be freeze-dried in the usual manner; depending on the need, excipients that provide for easy lyophilization, such as sugars (e.g. lactose, maltose and sucrose), sugar alcohols (e.g. mannitol and inositol), glycine and the like, may be added before freeze-drying is performed in the usual manner to make the intended preparations.
The production of the compounds of the present invention is described below in greater detail with reference to working examples but it should be understood that the invention is by no means limited by those examples.
For the purpose of showing the utility of the present invention, tests were conducted to evaluate the effectiveness of selected compounds of the formula (1) in inhibiting various types of NOS.